A scrubber for flue gas desulfurization which can have a diameter of several meters, can be provided with a scrubbing liquid sump above which an absorption zone free from baffles or packing can be formed. Above the absorption zone there is at least one nozzle plane which is formed with a nozzle assembly comprising a distributor, branch pipes from that distributor and nozzles connected to the branch pipes for dispensing the scrubbing liquid. The spray cones from these nozzles can overlap and the nozzles can be connected to the branch pipes by intermediate pipe sections.
The flue gas to be scrubbed can pass through the scrubber in the same direction as the scrubbing liquid, i.e. in uniflow or in an opposite direction to the scrubbing liquid, i.e. in counterflow. The preferred mode of operation is a counterflow with the scrubbing liquid passing upwardly through the absorption zone.
The conventional nozzle arrangement can have one or more such nozzle planes and the distributor in each of these nozzle planes can lie along a symmetry axis of the scrubbing column cross section with the branch pipes running to the right and to the left from the distributor or manifold symmetrically and equidistantly. The intermediate pipe sections and their nozzles are likewise symmetrically distributed over the cross section and the nozzle arrangement. Such a system with downwardly directed nozzles is described in GB A 2 297 705.
In this system, the spray cones of the nozzles overlap and the system is designed to cover the scrubbing column cross section as such as possible uniformly from a geometric point of view.
However, when concentration measurements are made in the scrubbing gas stream above the nozzle planes, it is found that, in spite of the effort to maintain a uniform spray distribution over the entire cross section, there are local regions of higher contaminant levels in the gas stream. Apparently the scrubbed gas contains bands or regions which are not contacted sufficiently with the scrubbing liquid in the absorption zone. These regions of insufficient absorption reduce the absorption efficiency and frequently require lengthening of the absorption zone or increased numbers of nozzle planes or increased numbers of nozzles in each nozzle plane, all of which substantially increases the amount of scrubbing liquid used, the operating gas for the increased pumping which is necessary and the increased capital cost. In fact, in many cases scrubbing columns cannot be retrofitted to eliminate this drawback.